138 HAWAIIAN AND OTHER PACIFIC ECHINI. 



Aceste weberi. 



Koehler, 1914. Ech. Indian Mus. Spat., p. 33. 



This species is based on the single specimen of Aceste taken by the Siboga. 

 It was secured off Rotti, D. E. I., in 510 fms. 



PALAEOPNEUSTIDAE A. Agassiz. 



The natural limitations of this family are still unknown. It must be 

 admitted that the general facies of the genera has been an important factor 

 in including them here for in the present state of our knowledge of their devel- 

 opment it is impossible to determine their right to be included. On the whole 

 the group as here deliminated seems fairly homogeneous and is certainly not 

 difficult to recognize. Most of the species are rare, deep-water forms, repre- 

 sented in museums by few specimens, and it is safe to say that a large series 

 of specimens of any one species does not exist in any museum. The genera 

 Palaeobrissus A. Agassiz and Meijerea Doderlein would seem to belong in the 

 family also, and they do, but the former is unquestionably based on adult 

 specimens of Palaeotropus josephinae, the growth-changes of which are very 

 interesting, while Meijerea seems to be undoubtedly a synonym of Argopata- 

 gus. The identity of these last two genera has been overlooked because atten- 

 tion has been directed to the relationship of Meijerea to Phryssocystis, while 

 Argopatagus has been quite ignored. Koehler's genus Paleotrema seems 

 based on a growth-stage of Palaeotropus (q. v.). 



The twelve genera here recognized as composing this family are distinguished 

 from each other by the presence or absence of marginal, peripetalous, and sub- 

 anal fascioles, by the shape of the test and the position of the periproct, and 

 by the tuberculation. The form and development of the petals are also of 

 service and the pedicellariae are of some value, but it must be granted that the 

 latter do not often help much in separating the genera. Globiferous pedicel- 

 lariae are found in only a few genera but tridentate and triphyllous are proba- 

 bly always present. The triphyllous are small and have leaf-shaped valves. 

 The tridentate show very great diversity and in several genera their modified 

 form, called rostrate pedicellariae, are well developed. The ophicephalous 

 are wanting in three genera and in several others have taken on distinctive forms. 

 The most remarkable of these is found in Phryssocysti- ami Argopatagus, and 

 is quite unlike any other pedicellaria I have seen. The Bpicuka in the tube- 

 feet are often abundant and occur in the form of more or less knobbed rods. 



